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RFXMod2 is an upgrade of RFXMod that will use a modified shell and mechanical structure in order to enhance plasma proximity to the shell and therefore to improve plasma control. The Control and Data Acquisition System for most of the plant systems and diagnostics previously used in RFXMod will be refurbished, while others will be completely re-built. The most important component that will be completely renewed is the Electromagnetic Probes (EM) data acquisition system. In the former system data acquisition and real-time control were implemented using two different technologies, i.e. CompactPCI and VME, respectively. In RFXMod2 a new architecture based on XILINX Zynq FPGA will be used to carry out at the same time both high-speed data acquisition and resampled data streaming for active plasma control. Moreover, numeric integration of EM signals will be carried out by the same FPGA supervising data acquisition and streaming. The use of MDSplus will be retained in RFXMod2, while the MARTe framework used for real-time plasma control will be replaced by MARTe2, a new framework developed under strict software quality standards. Plant control in RFXMod2 will be supervised by WinCC-OA, replacing the previous FactoryLink SCADA systems. Older plant units such as vacuum control using outdated S5 PLCs will be replaced by new systems, using OPC communication with the supervisory system. Old CAMAC equipment in diagnostics will be replaced by CompactPCI technology, making it uniform with the rest of the diagnostic data acquisition systems. Finally, specialized devices implemented in CAMAC such as timing sequence generators will be replaced by custom devices implemented using the same Zynq FPGA technology of the EM data acquisition devices.

An upgrade of RFX-­mod toroidal machine assembly is under development, aimed at widening the explored operational scenarios both in RFP and Tokamak configuration. The main design driver for this machine upgrade, named RFX-mod2, is the enhancement of the ‘shell-plasma proximity’, which is expected to provide a significant improvement in the plasma magnetic confinement. In order to achieve this goal, the existing Passive Stabilizing Shell will be adapted in order to be enclosed in the new vacuum vessel. This reconfiguration of the internal components of the experiment requires the design of a new structure aimed at supporting both the shell and the plasma facing components. The paper describes the design aspects of the shell assembly, with particular focus on the thermo-mechanical FEM analyses performed to verify the design of the components at the expected operating conditions.

The RFX-mod2 Nuclear Fusion experiment is an upgrade of RFX-mod. Among the other improvements in machine structure and diagnostics, a larger number of electromagnetic probes (EMs) is foreseen to provide more information about plasma instabilities and to allow an improved real-time plasma control. An Analog to Digital Converter (ADC) architecture able to provide both transient recording and real-time streaming is foreseen in RFX_mod2. Transient recording provides full speed data acquisition (up to 1 MSample/s) by recording data in local memory and reading memory content after the plasma discharge. Real-time streaming of subsampled data is required for active control. The chosen technology is based on the XILINX Zynq architecture that provides in the same chip a multicore ARM processor tightly couple to a FPGA. Time critical functions carried out by the FPGA in this context are: 1) The management of a circular data buffer and the DMA transfer in RAM of pre and post trigger samples after the trigger has been received; 2) Antialiasing filtering and subsampling of the samples to be streamed. The resulting samples are enqueued in a FIFO accessed by the processor. The functions carried out by the processor are: 1) The management of the configuration setting, received via TCP/IP or HTTP. The processor validates the configuration and write the appreciate registers in the FPGA; 2) Offline data readout of acquired samples in transient recording; 3) Network data streaming of subsampled data read from the FIFO and sent in UDP packets to the active plasma control system.